Rotating blowout preventer with independent cooling circuits and thrust bearing

CROSS-REFERENCE TO RELATED APPLICATIONS

0001This application is a divisional of U.S. patent application Ser. No. 10/423,105 filed Apr. 25, 2003 (U.S. Pat. No. 6,749,172) which is a divisional of U.S. patent application Ser. No. 09/735,385, filed Dec. 12, 2000 (U.S. Pat. No. 6,554,016) and claims the benefit of same.

STATEMENTS REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

0002Not applicable.

REFERENCE TO A MICROFICHE APPENDIX

0003Not applicable.

BACKGROUND OF THE INVENTION

Description of the Related Art

0004U.S. Pat. No. 5,178,215 serves as a starting point for the departure made by the present invention. The disclosure of U.S. Pat. No. 5,178,215 is incorporated herein by reference and includes a general discussion of an existing rotary blowout preventer which is fluid actuated to grip a drill pipe or kelly, and the controlled circulation of a fluid to lubricate and cool bearings and seals, and to filter particulate matter.

0005These existing rotary blowout preventers have an annulus between an outer housing and a rotary housing. Such systems use rather large bearings which require a rather large clearance. Such an arrangement has positive effects but also results in “wobbling” between the rotary housing and the outer housing. The wobbling creates heat, “nibbles” the seals, etc. A fluid is introduced into and circulates through the annulus between the outer housing and the rotary housing to cool the seal assemblies, the bearings and to counteract heat generated by contact between the seals and the rotary housing (wellhead fluid temperatures may normally be about 200° F., and during rotation, without cooling, the temperature would readily increase to about 350° F. and destroy a seal in a relatively short time). The circulated fluid also removes foreign particulate matter from the system. Pumps are used to maintain a fluid pressure in the annulus at a selected pressure differential above the well bore pressure.

0006The bearings in these rotary blowout preventers may normally operate at a temperature of about 250° F. Such bearings are subjected to a significant thrust load, e.g. 2,000 lbs.-force, due in part to an upward force created by well bore pressures and placed upon a packer assembly and a sleeve in the rotary housing. Such a thrust load will generate significant heat in a bearing rotating at, for example, 200 rpm. Heat, and heat over time, are important factors which may lead to bearing failure. For example, bearings may immediately fail if they reach temperatures of about 550° F. Even at temperatures of 250° F. a bearing may fail after a significant period of use, for example, twenty days of rotation at 200 rpm when subjected to a significant thrust load.

0007Such existing rotary blowout preventers are very functional at wellhead pressures up to 2000 psi. However, for reasons discussed herein, there are added challenges when wellhead pressures are in the range of, for example, 2500 psi to 5000 psi.

0008For example, as suggested, the continued and trouble free operability of such rotary blowout preventers is dependent, in part, upon the life of the seals and bearings within the rotary blowout preventer. The seals have a “pressure/velocity” or “pv” rating which may be used to predict the relative life of a seal given the pressure and velocity conditions to be borne by a seal. When considering “PV” rating, it is significant to note that a linear relationship does not exist between the life of a seal and the increases in pressure or rotational velocity to which a seal will be subjected. Rather, the life of the seal decreases exponentially as the pressure or rotational velocity to which the seal is subjected is increased.

0009As such, when well bore pressures increase to ranges from 2500 psi to 5000 psi, the loads, the wear and the heat exerted on seals and bearings within a rotary blowout preventer pose a greater challenge to the operations and life of the seals and bearings. This must be considered in the context of the fact that well bore operations may be shut down for maintenance work when significant wear of seals or bearings, significant “nibbling” of seals, or seal/bearing failure occurs. Such shut downs can significantly affect the profitability of well bore operations.

BRIEF SUMMARY OF THE INVENTION

0010This rotary blowout preventer has a first and a second pressurized fluid circuit. Each of the fluid circuits are defined into and out of a stationary body and between the stationary body, a rotating body, and two seals. The first fluid circuit is physically independent from the second fluid circuit although they share a seal interface. A fluid is introduced into the first fluid circuit at a pressure responsive to the well bore pressure. A fluid is introduced into the second fluid circuit at a pressure responsive to and lower than the pressure of the fluid in the first circuit. Adjustable orifices are connected to the outlet of the first and second fluid circuits to control such pressures within the circuits. Such pressures affect the wear rates of the seals. The system can therefore control the wear rate of one seal relative to another seal. A thrust bearing is added to share the load placed upon the upper bearings. The thrust bearing is connected between the top end of a packer sleeve and the stationary body.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

0011<figref idref="DRAWINGS">FIG. 1</figref> is a sectional view of a rotary blowout preventer incorporating the invention(s).

0012<figref idref="DRAWINGS">FIG. 2</figref> is a sectional view of the rotating body without the packer sleeve.

0013<figref idref="DRAWINGS">FIG. 3</figref> is an enlarged view of the middle and upper seal carriers shown in <figref idref="DRAWINGS">FIG. 1</figref>.

0014<figref idref="DRAWINGS">FIG. 4</figref> is a sectional view of the top closure.

0015<figref idref="DRAWINGS">FIG. 5</figref> is a schematic view of a control system which may be used in the invention(s).

DETAILED DESCRIPTION OF THE INVENTION

0016Referring to <figref idref="DRAWINGS">FIGS. 1 and 2</figref>, the rotating blowout preventer <b>8</b> generally includes a stationary body <b>10</b> which houses a rotating body <b>12</b>. The rotating body <b>12</b> includes a rotating housing <b>14</b>, a rotating housing cover plate <b>16</b> and a packer assembly <b>18</b>. The packer assembly <b>18</b> has a split keeper ring <b>20</b>, an outer packer <b>22</b>, an inner packer <b>24</b> and a packer sleeve <b>26</b>. The stationary body <b>10</b> generally includes a body <b>28</b> with a top closure <b>30</b> and a bottom closure flange <b>32</b>.

0017A lower bearing <b>34</b> is mounted between the stationary body <b>10</b> and the rotating body <b>12</b> in a cup <b>36</b>. An upper bearing <b>38</b> is mounted between the stationary body <b>10</b> and the rotating body <b>12</b> against a cup <b>40</b>. A bottom thrust bearing <b>42</b> is mounted between the stationary body <b>10</b> and the rotating body <b>12</b> on the bottom closure flange <b>32</b>.

0018A first or bottom seal carrier <b>44</b> is mounted between the stationary body <b>10</b> and the rotating body <b>12</b> and includes a groove for the mounting of a first seal <b>46</b>, which may, for example, be a seal of the type marketed by Kalsi Engineering, Inc. A bearing <b>48</b>, for example, a type marketed by Kaydon is mounted between the first seal carrier <b>44</b> and the rotating body <b>12</b>. A locking nut <b>50</b><i>a </i>may be used for attaching the bottom closure flange <b>32</b> to the body <b>28</b>.

0019Packer adapters <b>52</b> and <b>54</b> are connected to the packer sleeve <b>26</b>. A packer-pulling sleeve <b>56</b> engages the upper end of the packer adapter <b>54</b>. A thrust bearing <b>58</b> has a lower end <b>60</b> connected to a top end <b>62</b> of the packer sleeve of the rotating body <b>12</b>, and an upper end <b>64</b> connected to a top closure <b>66</b> of the stationary body <b>10</b>. The lower end <b>60</b> of the thrust bearing <b>58</b> is rotatable. The top closure <b>66</b> is held in place by a top closure flange <b>68</b> and studs <b>70</b>. The thrust bearing <b>58</b> is mounted inside a bearing retaining ring <b>72</b>. The bearing retaining ring <b>72</b> has openings between the thrust bearing o-rings <b>74</b> and <b>76</b> for introduction, circulation and outlet of a cooling fluid as part of a thrust bearing cooling and lubricating circuit <b>75</b>. The thrust bearing <b>58</b>, may be a commercially available thrust cylindrical roller bearing or it may be custom built.

0020The body <b>28</b> defines an inlet orifice <b>80</b> and an outlet orifice <b>82</b> of a first fluid or actuating, lubricating, cooling and filtering circuit <b>81</b>. The first fluid circuit <b>81</b> is further defined by the annular space between the rotating body <b>12</b> and the stationary body <b>10</b> and cools, lubricates and filters the region between the rotating body <b>12</b> and the stationary body <b>10</b> including the lower bearing <b>34</b> and the upper bearing <b>38</b>. <figref idref="DRAWINGS">FIG. 2</figref> shows surfaces <b>17</b><i>a </i>and <b>17</b><i>b </i>of the rotating housing cover plate <b>16</b> which help define the first fluid circuit <b>81</b> between the rotating body <b>12</b> and the second seal carrier <b>92</b>. <figref idref="DRAWINGS">FIG. 4</figref> shows annular cup <b>40</b> and annular surfaces <b>31</b><i>a,b </i>and <i>c </i>in top closure <b>30</b> which also define in part the first fluid circuit <b>81</b>. The first fluid circuit <b>81</b> loads first seal carrier <b>44</b> and one side of first seal <b>46</b> as well as second seal carrier <b>92</b> and one side of second seal <b>96</b>.

0021The rotating blowout preventer <b>8</b> has a second fluid or lubricating, cooling and filtering circuit <b>83</b>. The second fluid circuit <b>83</b> has an inlet orifice <b>84</b> and an outlet orifice <b>86</b> which may be tubular and which may be defined by the stationary body <b>10</b> such as by the body <b>28</b> and the top closure <b>30</b> and may be made, for example, by cross-drilled lines <b>88</b><i>a,b,c,d,e, </i>&amp; <i>f </i>in stationary body <b>10</b> and top closure <b>30</b>. The second fluid circuit <b>83</b> further has annular voids defined by the third seal carrier <b>94</b> itself, and between the third seal carrier <b>94</b> and annular channels <b>33</b><i>a </i>and <b>33</b><i>b </i>(<figref idref="DRAWINGS">FIG. 4</figref>) in top closure <b>30</b>. <figref idref="DRAWINGS">FIG. 2</figref> shows surface <b>17</b><i>c </i>of the rotating housing cover plate <b>16</b> which helps define the second fluid circuit <b>83</b> between the rotating body <b>12</b> and the third seal carrier <b>94</b>. The cross-drilled lines <b>88</b><i>b </i>and <b>88</b><i>e </i>may be isolated from the first fluid circuit by, for example, plugs <b>90</b><i>a </i>and <b>90</b><i>b </i>respectively.

0022As discussed above the annular voids defined intermediate top closure <b>30</b> and rotating housing cover plate <b>16</b> are for the mounting of a second or middle seal carrier <b>92</b> and a third or top seal carrier <b>94</b> (the first seal carrier <b>44</b> is placed in an annular void defined by rotating housing <b>14</b> and bottom closure flange <b>32</b>). A second seal <b>96</b> is mounted in the second seal carrier <b>92</b> and a third seal <b>98</b> is mounted in the third seal carrier <b>94</b>. The first, second and third seal carriers <b>44</b>, <b>92</b>, <b>94</b> are preferably hydraulically balanced floating seal carriers for carrying seals <b>46</b>, <b>96</b>, <b>98</b>. Such seals may be, for example, seals of the type marketed by Kalsi Engineering, Inc.

0023Referring to <figref idref="DRAWINGS">FIG. 3</figref> various seal or o-rings <b>100</b><i>a,b,c,d,e,f,g </i>and <i>h </i>are mounted in grooves around the second and third seal carriers <b>92</b> and <b>94</b>, and the top closure <b>30</b>. Bearing <b>102</b> is mounted in the second seal carrier <b>92</b> and in the first fluid circuit <b>81</b>. Bearing <b>104</b> is mounted in the second fluid circuit intermediate the third seal carrier <b>94</b> and a bearing spacer <b>101</b>. As discussed above, annular voids are defined by the top closure <b>30</b> and/or by the second and third seal carriers <b>92</b> and <b>94</b>. These annular voids form part of the first and the second fluid circuits <b>81</b> and <b>83</b>.

0024The rotating blowout preventer <b>8</b> and the fluid circulation circuits may be operated as discussed below. This system is especially useful in well bore environments where the pressure of the well bore exceeds 2500 psi on up to and exceeding 5000 psi.

0025The description following in the next two paragraphs serves as an example of the implementation of the invention and is not intended to quantify any limits on the value of features expressed in terms of pressure or time. However, such quantified values may be individually or collectively claimed as a preferred embodiment of the invention.

0026A fluid for actuating, for cooling, for lubricating and for removing foreign particulate matter is introduced into the first fluid circuit <b>81</b> at a pressure P<b>1</b>. The pressure P<b>1</b> is at or about well bore pressure plus about 300 psi (i.e. P<b>1</b> ranges from 300 psi to 5300 psi depending upon well bore pressure). At the same time, a like or a similar fluid is introduced into the second fluid circuit <b>83</b> at a pressure P<b>2</b> in the range of about 35% to 65% of the pressure P<b>1</b>. The second seal <b>96</b> experiences a pressure differential from P<b>1</b> to P<b>2</b> and the third seal <b>98</b> experiences a pressure differential from P<b>2</b> to atmosphere (or to the pressure of the thrust bearing cooling circuit <b>75</b>). The pressure P<b>2</b> may nominally be introduced into the second fluid circuit <b>83</b> at approximately one-half the pressure P<b>1</b>. Next, data may be gathered by one skilled in the rotating blow out preventer art relating to wear rates and conditions for bearings and seals within the rotary blowout preventer <b>8</b>. Then, such data may be used to empirically determine optimal pressure settings, pressure differentials and pressure changes to be made in response to variables such as changes in the well bore pressure in order to maintain the integrity of the seals and bearings. More specifically, it will be advantageous to control the pressure differentials such that the second seal <b>96</b> has a wear rate exceeding the wear rate of the third seal <b>98</b>. This is because if excessive wear is inflicted upon the second seal <b>96</b> prior to being inflicted upon the third seal <b>98</b>, a leak past the second seal <b>96</b> will create an increase in pressure in the second fluid circuit <b>83</b> as detected by controls such as pressure transducers, in the control system <b>110</b>. Then, the pressure increase detected in the second fluid circuit <b>83</b> may be used to infer or signal the possibility of the infliction of excessive wear on the third seal <b>98</b> (the timing of such an infliction of excessive wear on the third seal <b>98</b> being dependent upon a variety of variables such as well bore pressure, working rotational velocity, the current condition of the third seal <b>98</b>, etc.) thus prompting at least the consideration of maintenance operations. Accordingly, maintenance operations may be fore planned and fore scheduled prior to a leak past third seal <b>98</b>. Comparatively, the infliction of excessive wear on the third seal <b>98</b> prior to the infliction of excessive wear on the second seal <b>96</b> (or the infliction of excessive wear on the upper seal in the existing rotary blowout preventers) can result in a leak to atmosphere and an immediate shutdown or “kill” of well operations.

0027In a more specific example, if the well bore pressure is 4000 psi, then the pressure P<b>1</b> could be about 4300 psi, and the pressure P<b>2</b> could be nominally about 2150 psi (incidentally the pressure seen from above the third seal <b>98</b> could be about 60 psi). Then the pressures of the well bore, P<b>1</b> and P<b>2</b> can be detected (e.g., every fifty to one hundred milliseconds) in the control system <b>110</b> and the pressures P<b>1</b> and/or P<b>2</b> adjusted as suggested by empirical data or experience to, in anticipation of the infliction of excessive wear on a seal, cause the second seal <b>96</b> to incur excessive wear prior to the third seal <b>98</b>. As mentioned above, this sequence of events will suggest to operators that maintenance work should be planned and conducted within, and dependent upon operational variables, about six hours.

0028Referring to <figref idref="DRAWINGS">FIG. 5</figref>, a control system <b>110</b> which may be used with the rotary blowout preventer is shown. The control system <b>110</b> generally connects via line <b>112</b> to the inlet orifice <b>80</b> of the first fluid circuit <b>81</b> and via line <b>116</b> to the outlet orifice <b>82</b> of the first fluid circuit <b>81</b>. The control system <b>110</b> generally connects via line <b>114</b> to the inlet orifice <b>84</b> of the second fluid circuit <b>83</b> and via line <b>118</b> to the outlet orifice <b>86</b> of the second fluid circuit <b>83</b>. The control system <b>110</b> generally includes pumps <b>120</b> and <b>122</b> such as fixed displacement pumps for circulating a cooling and lubricating fluid; filters <b>124</b> and <b>126</b> for filtering the fluid fluid; and valves, for example, pinch valves, <b>128</b>, <b>130</b>, <b>132</b> and <b>134</b>. The valves may, for example, be used to create backpressure on the respective first and second fluid circuits <b>81</b>, <b>83</b> and to energize the floating seal carriers <b>46</b>, <b>96</b>, <b>98</b> by varying the orifice of the valves <b>128</b>, <b>130</b>, <b>132</b>, and <b>134</b>. The pressure within the circuits <b>81</b>, <b>83</b> may be independently adjusted or varied by other means, such as, for example, via pumps (not shown).

0029The thrust bearing <b>58</b> shares the thrust load, e.g. 2,000 lbs.-force, exerted by well bore pressure and placed upon the packer assembly <b>18</b> and consequently the load placed upon the lower and upper bearings <b>34</b>, <b>38</b> while allowing the rotable body <b>12</b> to rotate. Such results in lowering the heat on lower and upper bearings <b>34</b>, <b>38</b> and extending the life of same. By sharing the thrust load, “nibbling” of the first, second and third seals <b>46</b>, <b>96</b>, <b>98</b> may be decreased to extend the seal life of same. It is also advantageous to lubricate the thrust bearing <b>58</b> to counter the heat effects of the thrust load and rotation upon same. This may be accomplished, for example, by a thrust bearing cooling and lubricating circuit <b>75</b> which introduces the cooling fluid to the thrust bearing through the opening between the o-rings <b>74</b> and <b>76</b>.

0030It should be noted that reverse rotation may be utilized during use of the rotary blowout preventer <b>8</b> and the invention will be functional under such conditions.

0031In conclusion, therefore, it is seen that the present invention and the embodiments disclosed herein are well adapted to carry out the objectives and obtain the ends set forth. Certain changes can be made in the subject matter without departing from the spirit and the scope of this invention. It is realized that changes are possible within the scope of this invention and it is further intended that each element or step recited is to be understood as referring to all equivalent elements or steps. The description is intended to cover the invention as broadly as legally possible in whatever form it may be utilized.